The technology developed to provide a medium-power enhancement toPlessey's GaAs foundry MMIC (monolithic microwave IC) process and designcapability is described. These process improvements have been in twomajor areas, namely, the identification and optimization of an ionimplantation routine for power MESFET devices, and the development of asuitable heatsink technology compatible with the standard foundry ICprocess. Novel integral heatsink structures are developed which involvefabricating `bathtub-shaped' heatsinks under the FET. A range of powerFET devices fabricated using ion implanted material incorporating a p- compensating layer are characterized. The devices haveshown excellent performance in terms of gain, peripheral power density,and power added efficiency. These devices dissipate 20 watts of heatthrough the integral heatsink, thus clearly demonstrating theeffectiveness of the new heatsink technology. A method for fabricatingpower GaAs MMICs on a substrate of manageable thickness has thus beendemonstrated
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